Angiopoietin-2 (Ang-2) is a protein in the body which destabilizes blood vessels and is important in stimulating tumor blood vessels. There is evidence suggesting that Ang-2 may be important for the growth and progression of Glioblastoma multiforme (GBM). PF- 04856884 (CVX-060) is a compound which binds Ang-2 and prevents its activity. The hypothesis is that PF-04856884 will be safe and effective in patients with recurrent Glioblastoma multiforme (GBM).